1. Field of the Invention
This invention relates to the making of flat glass by a continuous process wherein glass is formed as a continuous sheet while being conveyed along the surface of a pool of molten metal. More particularly, this invention relates to an improved method for delivering molten glass from a glass melting and refining furnace to a glass forming chamber.
2. Description of the Prior Art
It has been known to form flat glass by delivering molten glass onto a pool of molten metal and cooling the glass to form a dimensionally stable, continuous sheet of glass while it is in contact with molten metal and then removing the continuous sheet of glass from the molten metal. U.S. Pat. No. 789,911 to Hitchcock shows horizontal delivery of molten glass onto a pool of molten metal in an enclosed chamber for forming a continuous sheet of flat glass. The art of manufacturing flat glass by floating glass on molten metal has developed since the time of Hitchcock in the manner disclosed by Pilkington in U.S. Pat. Nos. 3,083,551 and 3,220,816. In these processes, molten glass is poured downward onto a pool of molten metal and is allowed to spread in a laterally unhindered fashion outward from the location where it is poured onto the molten metal. It flows both laterally and rearwardly with respect to the general movement of glass along the surface of molten metal as it is drawn and cooled to form a dimensionally stable, continuous sheet of glass.
In the processes of glass forming involving the pouring of molten glass downward onto a pool of molten metal, there have been various developments and improvements in the delivery of molten glass onto the pool of molten metal. In particular, it has been proposed that the stream of glass flowing over a lip and downward onto a pool of molten metal be a stream that is deeper in its central portion than in its edge portions in order to provide an adequate flow of molten glass in the central region of the stream to satisfy both the rearward flow of glass on the molten tin and the forward central flow of molten glass on the molten tin. This is shown in U.S. Pat. No. 3,351,452 to Robinson. A further improvement of the method and apparatus of Robinson is shown in U.S. Pat. No. 3,576,612 to Prislan wherein a concave-shaped tweel is provided with means for differentially heating it across its transverse width.
When molten glass is directly delivered horizontally onto a pool of molten metal, it has been found that if the glass is relatively rapidly cooled and attenuated in a short distance extending down the stream from the point of delivery onto the molten metal, the continuous sheet that is formed may have a non-uniform transverse thickness. This may be avoided by carrying out the process in the manner described in the parent of this application wherein differential transverse heating of the body of glass downstream of its point of delivery onto a pool of molten tin is accomplished in order to provide for a substantially flat velocity profile in the stream of glass. The present invention contemplates an improved structure for delivering molten glass along a horizontal path onto molten metal for forming and an improved method for carrying out such delivery of molten glass onto molten metal so that a dimensionally stable ribbon of glass may be established within a short distance downstream from the point of delivery with the continuous sheet of glass so formed having a uniform transverse thickness.